A cylinder is a mechanical device that produces linear motion. A hydraulic cylinder is powered by pressurized hydraulic fluid, which typically is supplied to the cylinder from a hydraulic pump, or hydraulic power unit. Hydraulic fluid or oil is generally considered an incompressible fluid, which delivers smooth motion and operating characteristics to the cylinder.
During assembly of the cylinder, or installing the cylinder into the apparatus or machinery it serves, air may be introduced into the cylinder body, or entrained in the cylinder oil. Air is a compressible fluid, and when used in a hydraulic system operating at elevated pressures, the trapped air can cause erratic behavior or undesirable motion, which can have detrimental effects on the machinery, cause unsafe conditions for workers, and cause damage to the components of the hydraulic system. It is desirable for air to be removed from the hydraulic oil before operating the machinery as intended. In single stage cylinders, this is generally accomplished by cycling the cylinder from fully retracted to fully extended positions, flushing any air out of the cylinder via the hydraulic oil, back to the hydraulic power unit, where the air is removed by various hydraulic devices.
Telescopic cylinders, also known as multi-stage cylinders, have a unique design where multiple stages are nested together in a compact design, and when deployed greatly increase the extended length of the cylinder. These telescopic designs have multiple areas within the cylinder that may trap air that is entrained or present within the hydraulic fluid. This trapped air within the cylinder may cause erratic behavior in the cylinder movement or performance, and should be removed from the cylinder as much as possible, in order to allow the cylinder to display smooth, predictable motion.
There exists a number of products and methods to bleed air from hydraulic cylinders. Examples of such products include a Minimess® fittings or test couplings, bleeder screws, bleeder screws with adapters, and pan head screws with face seal. These existing types of air bleed devices and methods of use thereof have positive and negative attributes. On the positive side, these types of air bleed devices and methods:                a. include a number of various designs, sizes, connection types, materials that are available for use;        b. are readily available and inexpensive to purchase;        c. are known to the industry, have a proven history, and are simple to use; and        d. can be installed in multiple locations in the hydraulic cylinder, targeting areas in which air is likely to collect and become trapped.        
On the negative side, these types of air bleed devices and methods:                a. oftentimes require manual labor to open and close the valve, sometimes in awkward or dangerous positions, and sometimes require multiple people to complete the air bleed process;        b. may be under high pressure, and when opened, can release pressure in the vicinity of the operator, causing a safety hazard;        c. possibly can allow contaminants into the cylinder or hydraulic system while opening a valve, and thus exposing the hydraulic fluid to the environment and surrounding atmosphere;        d. allow both air and oil to escape, often into a rudimentary collection pail or similar container, which may be difficult to handle—for example, within the cylinder, typically there does not exist a definite separation between the air and oil, but more so a mixture of the two, or sometimes a foamy consistency, and consequently sometimes a substantial amount of air and oil mixture must be bled from the cylinder to ensure removal of all air—these bled fluids must be disposed of in an environmentally safe manner;        e. may cause an environmental hazard if oil is spilled or uncontained/captures; and        f. the air bleeding process may cause the cylinder to move with operators in the area, potentially in hazardous positions or locations.        
In a typical hydraulic cylinder with a commercially available bleeder screw installed, air entrapped within the hydraulic oil in the cylinder would naturally rise to the top of the fluid volume. The air bleed valve is strategically placed in a location to remove this air. The air bleed valve is opened manually, releasing the pressurized oil and air mixture. In this case, the operator would need to be ready with some method to capture this released fluid. Moreover, if a large enough volume of air was in the cylinder, the cylinder would need to be actuated to “push” this air out of the cylinder.
Accordingly, a need exists in the art for a device and method to remove air from a hydraulic cylinder of the type described herein that overcomes one or more of the deficiencies with known devices and methods of bleeding air from such cylinder(s).